SEOUL — Amid escalating tensions in the Korean Peninsula, South Korean President Moon Jae-In sought Russian backing Wednesday for calls to block critical crude oil supplies to the North Korean regime after its latest nuclear test.

Moon’s request was met with reluctance from Russian President Vladimir Putin, however, who condemned the North’s tests but urged diplomatic talks.

Putin’s stance underscored the challenges for the West and its allies to win U.N. Security Council approval for tougher economic pressures on the North. Russia and China — both permanent Security Council members — have criticized North Korea’s defiance over its nuclear and missile tests, but appear to emphasize diplomatic outreach rather than more sanctions.

The newly elected South Korean president has requested the U.N. Security Council consider tough new sanctions on North Korea to block its sources of foreign income, including cutting off its crude oil supply and banning its workers from being sent abroad.

During an economic summit Wednesday in Vladivostok, Russia, Moon urged Putin and Chinese President Xi Jinping to support intensifying U.N. sanctions on North Korea to at least bring North Korea on a track to dialogue, Moon’s spokesman Yoon Young-chan said.

“The president asked Russia to help, noting it was imperative to at least cut off oil supplies to North Korea this time,” the spokesman said.

About 90 percent of North Korean trade goes through China, which is also North Korea’s main source of fuel. But China does not publicly disclose details about its oil exports to North Korea. The U.S. Energy Information Administration estimated that North Korea imports about 10,000 barrels per day.

Moon noted that North Korea was once forced to multilateral negotiations after China cut off its oil supplies for three days in 2003 in response to nuclear tests. At the time, China said the suspension was necessary for technical reasons, but was also meant as a “tough message.”

However, analysts have said China would be reluctant to agree to sanctions that could seriously destabilize its North Korean client state — such as cutting off oil permanently or for a significant period of time — because China’s primary concern is stability on its borders.

Sanctions have done little to alter North Korean behavior, or stop it from building up its nuclear and missile program. In response to two North Korean intercontinental ballistic missile tests in July, the U.N. Security Council unanimously imposed bans on various North Korean exports, including coal, iron and seafood.

North Korea conducted its sixth and most powerful nuclear test to date on Sunday, detonating a device that it claimed was a hydrogen bomb designed to be carried by a long-range missile capable of reaching mainland United States.

South Korean officials have also reported signs of another missile test in the works, possibly a long-range launch set for this weekend.

At a joint news conference following his meeting with Moon, Putin condemned North Korea’s tests, calling Pyongyang’s missile and nuclear program a “crude violation of U.N. Security Council resolutions, undermines the nonproliferation regime and creates a threat to the security of northeastern Asia.”

But Putin was reluctant to support Moon’s push for harsher sanctions.

“However, I am concerned cutting off oil supplies to North Korea may cause damage to people in hospitals or other ordinary citizens,” Putin added, according Yoon’s briefing to reporters.

Putin maintained it was impossible to resolve the North Korean crisis with sanctions and pressure alone, and urged diplomatic solutions.